Fiber-optic sensors have been extensively developed for many applications over the past two decades. Chemical sensors utilizing optical fibers may be fabricated from single or multimode fibers, and may be used for measurement of gases, ions, pH and organic chemicals.
The use of optical fiber as an extrinsic sensor (in which an optical fiber is only used as a transportation medium for light) for oxygen concentration presents a unique opportunity in environmental monitoring, biotechnology process control and aquaculture process control. When compared with Clark-type oxygen sensors, fiber-optic oxygen sensors have the advantage of fast response time, light weight, remotely operable, low maintenance and potentially low cost. However, the use of fluorescence intensity in a fiber-optic oxygen sensor is hampered by problems associated with optical fiber bending loss.
Recent progress in referencing techniques for intensity based optical fiber sensors has been reviewed by MURTAZA and SENIOR, and ratiometric technique such as dual-wavelength referencing configuration has been used to reduce the effect of fiber bending loss.